2.6. Configuration Files

2.6.1. hbase-site.xml and hbase-default.xml

Just as in Hadoop where you add site-specific HDFS configuration to the hdfs-site.xml file, for HBase, site specific customizations go into the file conf/hbase-site.xml. For the list of configurable properties, see Section 2.6.1.1, “HBase Default Configuration” below or view the raw hbase-default.xml source file in the HBase source code at src/main/resources.

Not all configuration options make it out to hbase-default.xml. Configuration that it is thought rare anyone would change can exist only in code; the only way to turn up such configurations is via a reading of the source code itself.

Currently, changes here will require a cluster restart for HBase to notice the change.

2.6.1.1. HBase Default Configuration

HBase Default Configuration

The documentation below is generated using the default hbase configuration file, hbase-default.xml, as source.

hbase.rootdir

The directory shared by region servers and into which HBase persists. The URL should be 'fully-qualified' to include the filesystem scheme. For example, to specify the HDFS directory '/hbase' where the HDFS instance's namenode is running at namenode.example.org on port 9000, set this value to: hdfs://namenode.example.org:9000/hbase. By default HBase writes into /tmp. Change this configuration else all data will be lost on machine restart.

Default: file:///tmp/hbase-${user.name}/hbase

hbase.master.port

The port the HBase Master should bind to.

Default: 60000

hbase.cluster.distributed

The mode the cluster will be in. Possible values are false for standalone mode and true for distributed mode. If false, startup will run all HBase and ZooKeeper daemons together in the one JVM.

Default: false

hbase.tmp.dir

Temporary directory on the local filesystem. Change this setting to point to a location more permanent than '/tmp' (The '/tmp' directory is often cleared on machine restart).

Default: /tmp/hbase-${user.name}

hbase.master.info.port

The port for the HBase Master web UI. Set to -1 if you do not want a UI instance run.

Default: 60010

hbase.master.info.bindAddress

The bind address for the HBase Master web UI

Default: 0.0.0.0

hbase.client.write.buffer

Default size of the HTable clien write buffer in bytes. A bigger buffer takes more memory -- on both the client and server side since server instantiates the passed write buffer to process it -- but a larger buffer size reduces the number of RPCs made. For an estimate of server-side memory-used, evaluate hbase.client.write.buffer * hbase.regionserver.handler.count

Default: 2097152

hbase.regionserver.port

The port the HBase RegionServer binds to.

Default: 60020

hbase.regionserver.info.port

The port for the HBase RegionServer web UI Set to -1 if you do not want the RegionServer UI to run.

Default: 60030

hbase.regionserver.info.port.auto

Whether or not the Master or RegionServer UI should search for a port to bind to. Enables automatic port search if hbase.regionserver.info.port is already in use. Useful for testing, turned off by default.

Default: false

hbase.regionserver.info.bindAddress

The address for the HBase RegionServer web UI

Default: 0.0.0.0

hbase.regionserver.class

The RegionServer interface to use. Used by the client opening proxy to remote region server.

Default: org.apache.hadoop.hbase.ipc.HRegionInterface

hbase.client.pause

General client pause value. Used mostly as value to wait before running a retry of a failed get, region lookup, etc.

Default: 1000

hbase.client.retries.number

Maximum retries. Used as maximum for all retryable operations such as fetching of the root region from root region server, getting a cell's value, starting a row update, etc. Default: 10.

Default: 10

hbase.bulkload.retries.number

Maximum retries. This is maximum number of iterations to atomic bulk loads are attempted in the face of splitting operations 0 means never give up. Default: 0.

Default: 0

hbase.client.scanner.caching

Number of rows that will be fetched when calling next on a scanner if it is not served from (local, client) memory. Higher caching values will enable faster scanners but will eat up more memory and some calls of next may take longer and longer times when the cache is empty. Do not set this value such that the time between invocations is greater than the scanner timeout; i.e. hbase.regionserver.lease.period

Default: 1

hbase.client.keyvalue.maxsize

Specifies the combined maximum allowed size of a KeyValue instance. This is to set an upper boundary for a single entry saved in a storage file. Since they cannot be split it helps avoiding that a region cannot be split any further because the data is too large. It seems wise to set this to a fraction of the maximum region size. Setting it to zero or less disables the check.

Default: 10485760

hbase.regionserver.lease.period

HRegion server lease period in milliseconds. Default is 60 seconds. Clients must report in within this period else they are considered dead.

Default: 60000

hbase.regionserver.handler.count

Count of RPC Listener instances spun up on RegionServers. Same property is used by the Master for count of master handlers. Default is 10.

Default: 10

hbase.regionserver.msginterval

Interval between messages from the RegionServer to Master in milliseconds.

Default: 3000

hbase.regionserver.optionallogflushinterval

Sync the HLog to the HDFS after this interval if it has not accumulated enough entries to trigger a sync. Default 1 second. Units: milliseconds.

Default: 1000

hbase.regionserver.regionSplitLimit

Limit for the number of regions after which no more region splitting should take place. This is not a hard limit for the number of regions but acts as a guideline for the regionserver to stop splitting after a certain limit. Default is set to MAX_INT; i.e. do not block splitting.

Default: 2147483647

hbase.regionserver.logroll.period

Period at which we will roll the commit log regardless of how many edits it has.

Default: 3600000

hbase.regionserver.logroll.errors.tolerated

The number of consecutive WAL close errors we will allow before triggering a server abort. A setting of 0 will cause the region server to abort if closing the current WAL writer fails during log rolling. Even a small value (2 or 3) will allow a region server to ride over transient HDFS errors.

Default: 2

hbase.regionserver.hlog.reader.impl

The HLog file reader implementation.

Default: org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogReader

hbase.regionserver.hlog.writer.impl

The HLog file writer implementation.

Default: org.apache.hadoop.hbase.regionserver.wal.SequenceFileLogWriter

hbase.regionserver.nbreservationblocks

The number of resevoir blocks of memory release on OOME so we can cleanup properly before server shutdown.

Default: 4

hbase.zookeeper.dns.interface

The name of the Network Interface from which a ZooKeeper server should report its IP address.

Default: default

hbase.zookeeper.dns.nameserver

The host name or IP address of the name server (DNS) which a ZooKeeper server should use to determine the host name used by the master for communication and display purposes.

Default: default

hbase.regionserver.dns.interface

The name of the Network Interface from which a region server should report its IP address.

Default: default

hbase.regionserver.dns.nameserver

The host name or IP address of the name server (DNS) which a region server should use to determine the host name used by the master for communication and display purposes.

Default: default

hbase.master.dns.interface

The name of the Network Interface from which a master should report its IP address.

Default: default

hbase.master.dns.nameserver

The host name or IP address of the name server (DNS) which a master should use to determine the host name used for communication and display purposes.

Default: default

hbase.balancer.period

Period at which the region balancer runs in the Master.

Default: 300000

hbase.regions.slop

Rebalance if any regionserver has average + (average * slop) regions. Default is 20% slop.

Default: 0.2

hbase.master.logcleaner.ttl

Maximum time a HLog can stay in the .oldlogdir directory, after which it will be cleaned by a Master thread.

Default: 600000

hbase.master.logcleaner.plugins

A comma-separated list of LogCleanerDelegate invoked by the LogsCleaner service. These WAL/HLog cleaners are called in order, so put the HLog cleaner that prunes the most HLog files in front. To implement your own LogCleanerDelegate, just put it in HBase's classpath and add the fully qualified class name here. Always add the above default log cleaners in the list.

Default: org.apache.hadoop.hbase.master.TimeToLiveLogCleaner

hbase.regionserver.global.memstore.upperLimit

Maximum size of all memstores in a region server before new updates are blocked and flushes are forced. Defaults to 40% of heap

Default: 0.4

hbase.regionserver.global.memstore.lowerLimit

When memstores are being forced to flush to make room in memory, keep flushing until we hit this mark. Defaults to 35% of heap. This value equal to hbase.regionserver.global.memstore.upperLimit causes the minimum possible flushing to occur when updates are blocked due to memstore limiting.

Default: 0.35

hbase.server.thread.wakefrequency

Time to sleep in between searches for work (in milliseconds). Used as sleep interval by service threads such as log roller.

Default: 10000

hbase.server.versionfile.writeattempts

How many time to retry attempting to write a version file before just aborting. Each attempt is seperated by the hbase.server.thread.wakefrequency milliseconds.

Default: 3

hbase.hregion.memstore.flush.size

Memstore will be flushed to disk if size of the memstore exceeds this number of bytes. Value is checked by a thread that runs every hbase.server.thread.wakefrequency.

Default: 134217728

hbase.hregion.preclose.flush.size

If the memstores in a region are this size or larger when we go to close, run a "pre-flush" to clear out memstores before we put up the region closed flag and take the region offline. On close, a flush is run under the close flag to empty memory. During this time the region is offline and we are not taking on any writes. If the memstore content is large, this flush could take a long time to complete. The preflush is meant to clean out the bulk of the memstore before putting up the close flag and taking the region offline so the flush that runs under the close flag has little to do.

Default: 5242880

hbase.hregion.memstore.block.multiplier

Block updates if memstore has hbase.hregion.block.memstore time hbase.hregion.flush.size bytes. Useful preventing runaway memstore during spikes in update traffic. Without an upper-bound, memstore fills such that when it flushes the resultant flush files take a long time to compact or split, or worse, we OOME.

Default: 2

hbase.hregion.memstore.mslab.enabled

Enables the MemStore-Local Allocation Buffer, a feature which works to prevent heap fragmentation under heavy write loads. This can reduce the frequency of stop-the-world GC pauses on large heaps.

Default: true

hbase.hregion.max.filesize

Maximum HStoreFile size. If any one of a column families' HStoreFiles has grown to exceed this value, the hosting HRegion is split in two. Default: 10G.

Default: 10737418240

hbase.hstore.compactionThreshold

If more than this number of HStoreFiles in any one HStore (one HStoreFile is written per flush of memstore) then a compaction is run to rewrite all HStoreFiles files as one. Larger numbers put off compaction but when it runs, it takes longer to complete.

Default: 3

hbase.hstore.blockingStoreFiles

If more than this number of StoreFiles in any one Store (one StoreFile is written per flush of MemStore) then updates are blocked for this HRegion until a compaction is completed, or until hbase.hstore.blockingWaitTime has been exceeded.

Default: 7

hbase.hstore.blockingWaitTime

The time an HRegion will block updates for after hitting the StoreFile limit defined by hbase.hstore.blockingStoreFiles. After this time has elapsed, the HRegion will stop blocking updates even if a compaction has not been completed. Default: 90 seconds.

Default: 90000

hbase.hstore.compaction.max

Max number of HStoreFiles to compact per 'minor' compaction.

Default: 10

hbase.hregion.majorcompaction

The time (in miliseconds) between 'major' compactions of all HStoreFiles in a region. Default: 1 day. Set to 0 to disable automated major compactions.

Default: 86400000

hbase.mapreduce.hfileoutputformat.blocksize

The mapreduce HFileOutputFormat writes storefiles/hfiles. This is the minimum hfile blocksize to emit. Usually in hbase, writing hfiles, the blocksize is gotten from the table schema (HColumnDescriptor) but in the mapreduce outputformat context, we don't have access to the schema so get blocksize from Configuration. The smaller you make the blocksize, the bigger your index and the less you fetch on a random-access. Set the blocksize down if you have small cells and want faster random-access of individual cells.

Default: 65536

hfile.block.cache.size

Percentage of maximum heap (-Xmx setting) to allocate to block cache used by HFile/StoreFile. Default of 0.25 means allocate 25%. Set to 0 to disable but it's not recommended.

Default: 0.25

hbase.hash.type

The hashing algorithm for use in HashFunction. Two values are supported now: murmur (MurmurHash) and jenkins (JenkinsHash). Used by bloom filters.

Default: murmur

hfile.block.index.cacheonwrite

This allows to put non-root multi-level index blocks into the block cache at the time the index is being written.

Default: false

hfile.index.block.max.size

When the size of a leaf-level, intermediate-level, or root-level index block in a multi-level block index grows to this size, the block is written out and a new block is started.

Default: 131072

hfile.format.version

The HFile format version to use for new files. Set this to 1 to test backwards-compatibility. The default value of this option should be consistent with FixedFileTrailer.MAX_VERSION.

Default: 2

io.storefile.bloom.block.size

The size in bytes of a single block ("chunk") of a compound Bloom filter. This size is approximate, because Bloom blocks can only be inserted at data block boundaries, and the number of keys per data block varies.

Default: 131072

io.storefile.bloom.cacheonwrite

Enables cache-on-write for inline blocks of a compound Bloom filter.

Default: false

hbase.rs.cacheblocksonwrite

Whether an HFile block should be added to the block cache when the block is finished.

Default: false

hbase.rpc.engine

Implementation of org.apache.hadoop.hbase.ipc.RpcEngine to be used for client / server RPC call marshalling.

Default: org.apache.hadoop.hbase.ipc.WritableRpcEngine

hbase.master.keytab.file

Full path to the kerberos keytab file to use for logging in the configured HMaster server principal.

Default:

hbase.master.kerberos.principal

Ex. "hbase/_HOST@EXAMPLE.COM". The kerberos principal name that should be used to run the HMaster process. The principal name should be in the form: user/hostname@DOMAIN. If "_HOST" is used as the hostname portion, it will be replaced with the actual hostname of the running instance.

Default:

hbase.regionserver.keytab.file

Full path to the kerberos keytab file to use for logging in the configured HRegionServer server principal.

Default:

hbase.regionserver.kerberos.principal

Ex. "hbase/_HOST@EXAMPLE.COM". The kerberos principal name that should be used to run the HRegionServer process. The principal name should be in the form: user/hostname@DOMAIN. If "_HOST" is used as the hostname portion, it will be replaced with the actual hostname of the running instance. An entry for this principal must exist in the file specified in hbase.regionserver.keytab.file

Default:

hadoop.policy.file

The policy configuration file used by RPC servers to make authorization decisions on client requests. Only used when HBase security is enabled.

Default: hbase-policy.xml

hbase.superuser

List of users or groups (comma-separated), who are allowed full privileges, regardless of stored ACLs, across the cluster. Only used when HBase security is enabled.

Default:

hbase.auth.key.update.interval

The update interval for master key for authentication tokens in servers in milliseconds. Only used when HBase security is enabled.

Default: 86400000

hbase.auth.token.max.lifetime

The maximum lifetime in milliseconds after which an authentication token expires. Only used when HBase security is enabled.

Default: 604800000

zookeeper.session.timeout

ZooKeeper session timeout. HBase passes this to the zk quorum as suggested maximum time for a session (This setting becomes zookeeper's 'maxSessionTimeout'). See http://hadoop.apache.org/zookeeper/docs/current/zookeeperProgrammers.html#ch_zkSessions "The client sends a requested timeout, the server responds with the timeout that it can give the client. " In milliseconds.

Default: 180000

zookeeper.znode.parent

Root ZNode for HBase in ZooKeeper. All of HBase's ZooKeeper files that are configured with a relative path will go under this node. By default, all of HBase's ZooKeeper file path are configured with a relative path, so they will all go under this directory unless changed.

Default: /hbase

zookeeper.znode.rootserver

Path to ZNode holding root region location. This is written by the master and read by clients and region servers. If a relative path is given, the parent folder will be ${zookeeper.znode.parent}. By default, this means the root location is stored at /hbase/root-region-server.

Default: root-region-server

zookeeper.znode.acl.parent

Root ZNode for access control lists.

Default: acl

hbase.coprocessor.region.classes

A comma-separated list of Coprocessors that are loaded by default on all tables. For any override coprocessor method, these classes will be called in order. After implementing your own Coprocessor, just put it in HBase's classpath and add the fully qualified class name here. A coprocessor can also be loaded on demand by setting HTableDescriptor.

Default:

hbase.coprocessor.master.classes

A comma-separated list of org.apache.hadoop.hbase.coprocessor.MasterObserver coprocessors that are loaded by default on the active HMaster process. For any implemented coprocessor methods, the listed classes will be called in order. After implementing your own MasterObserver, just put it in HBase's classpath and add the fully qualified class name here.

Default:

hbase.zookeeper.quorum

Comma separated list of servers in the ZooKeeper Quorum. For example, "host1.mydomain.com,host2.mydomain.com,host3.mydomain.com". By default this is set to localhost for local and pseudo-distributed modes of operation. For a fully-distributed setup, this should be set to a full list of ZooKeeper quorum servers. If HBASE_MANAGES_ZK is set in hbase-env.sh this is the list of servers which we will start/stop ZooKeeper on.

Default: localhost

hbase.zookeeper.peerport

Port used by ZooKeeper peers to talk to each other. See http://hadoop.apache.org/zookeeper/docs/r3.1.1/zookeeperStarted.html#sc_RunningReplicatedZooKeeper for more information.

Default: 2888

hbase.zookeeper.leaderport

Port used by ZooKeeper for leader election. See http://hadoop.apache.org/zookeeper/docs/r3.1.1/zookeeperStarted.html#sc_RunningReplicatedZooKeeper for more information.

Default: 3888

hbase.zookeeper.property.initLimit

Property from ZooKeeper's config zoo.cfg. The number of ticks that the initial synchronization phase can take.

Default: 10

hbase.zookeeper.property.syncLimit

Property from ZooKeeper's config zoo.cfg. The number of ticks that can pass between sending a request and getting an acknowledgment.

Default: 5

hbase.zookeeper.property.dataDir

Property from ZooKeeper's config zoo.cfg. The directory where the snapshot is stored.

Default: ${hbase.tmp.dir}/zookeeper

hbase.zookeeper.property.clientPort

Property from ZooKeeper's config zoo.cfg. The port at which the clients will connect.

Default: 2181

hbase.zookeeper.property.maxClientCnxns

Property from ZooKeeper's config zoo.cfg. Limit on number of concurrent connections (at the socket level) that a single client, identified by IP address, may make to a single member of the ZooKeeper ensemble. Set high to avoid zk connection issues running standalone and pseudo-distributed.

Default: 300

hbase.rest.port

The port for the HBase REST server.

Default: 8080

hbase.rest.readonly

Defines the mode the REST server will be started in. Possible values are: false: All HTTP methods are permitted - GET/PUT/POST/DELETE. true: Only the GET method is permitted.

Default: false

hbase.defaults.for.version.skip

Set to true to skip the 'hbase.defaults.for.version' check. Setting this to true can be useful in contexts other than the other side of a maven generation; i.e. running in an ide. You'll want to set this boolean to true to avoid seeing the RuntimException complaint: "hbase-default.xml file seems to be for and old version of HBase (@@@VERSION@@@), this version is X.X.X-SNAPSHOT"

Default: false

hbase.coprocessor.abortonerror

Set to true to cause the hosting server (master or regionserver) to abort if a coprocessor throws a Throwable object that is not IOException or a subclass of IOException. Setting it to true might be useful in development environments where one wants to terminate the server as soon as possible to simplify coprocessor failure analysis.

Default: false

hbase.online.schema.update.enable

Set true to enable online schema changes. This is an experimental feature. There are known issues modifying table schemas at the same time a region split is happening so your table needs to be quiescent or else you have to be running with splits disabled.

Default: false

dfs.support.append

Does HDFS allow appends to files? This is an hdfs config. set in here so the hdfs client will do append support. You must ensure that this config. is true serverside too when running hbase (You will have to restart your cluster after setting it).

Default: true

hbase.thrift.minWorkerThreads

The "core size" of the thread pool. New threads are created on every connection until this many threads are created.

Default: 16

hbase.thrift.maxWorkerThreads

The maximum size of the thread pool. When the pending request queue overflows, new threads are created until their number reaches this number. After that, the server starts dropping connections.

Default: 1000

hbase.thrift.maxQueuedRequests

The maximum number of pending Thrift connections waiting in the queue. If there are no idle threads in the pool, the server queues requests. Only when the queue overflows, new threads are added, up to hbase.thrift.maxQueuedRequests threads.

Default: 1000

hbase.offheapcache.percentage

The amount of off heap space to be allocated towards the experimental off heap cache. If you desire the cache to be disabled, simply set this value to 0.

Default: 0

hbase.data.umask.enable

Enable, if true, that file permissions should be assigned to the files written by the regionserver

Default: false

hbase.data.umask

File permissions that should be used to write data files when hbase.data.umask.enable is true

Default: 000

hbase.metrics.showTableName

Whether to include the prefix "tbl.tablename" in per-column family metrics. If true, for each metric M, per-cf metrics will be reported for tbl.T.cf.CF.M, if false, per-cf metrics will be aggregated by column-family across tables, and reported for cf.CF.M. In both cases, the aggregated metric M across tables and cfs will be reported.

Default: true

2.6.2. hbase-env.sh

Set HBase environment variables in this file. Examples include options to pass the JVM on start of an HBase daemon such as heap size and garbarge collector configs. You can also set configurations for HBase configuration, log directories, niceness, ssh options, where to locate process pid files, etc. Open the file at conf/hbase-env.sh and peruse its content. Each option is fairly well documented. Add your own environment variables here if you want them read by HBase daemons on startup.

Changes here will require a cluster restart for HBase to notice the change.

2.6.3. log4j.properties

Edit this file to change rate at which HBase files are rolled and to change the level at which HBase logs messages.

Changes here will require a cluster restart for HBase to notice the change though log levels can be changed for particular daemons via the HBase UI.

2.6.4. Client configuration and dependencies connecting to an HBase cluster

Since the HBase Master may move around, clients bootstrap by looking to ZooKeeper for current critical locations. ZooKeeper is where all these values are kept. Thus clients require the location of the ZooKeeper ensemble information before they can do anything else. Usually this the ensemble location is kept out in the hbase-site.xml and is picked up by the client from the CLASSPATH.

If you are configuring an IDE to run a HBase client, you should include the conf/ directory on your classpath so hbase-site.xml settings can be found (or add src/test/resources to pick up the hbase-site.xml used by tests).

Minimally, a client of HBase needs the hbase, hadoop, log4j, commons-logging, commons-lang, and ZooKeeper jars in its CLASSPATH connecting to a cluster.

An example basic hbase-site.xml for client only might look as follows:

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
  <property>
    <name>hbase.zookeeper.quorum</name>
    <value>example1,example2,example3</value>
    <description>The directory shared by region servers.
    </description>
  </property>
</configuration>

2.6.4.1. Java client configuration

The configuration used by a Java client is kept in an HBaseConfiguration instance. The factory method on HBaseConfiguration, HBaseConfiguration.create();, on invocation, will read in the content of the first hbase-site.xml found on the client's CLASSPATH, if one is present (Invocation will also factor in any hbase-default.xml found; an hbase-default.xml ships inside the hbase.X.X.X.jar). It is also possible to specify configuration directly without having to read from a hbase-site.xml. For example, to set the ZooKeeper ensemble for the cluster programmatically do as follows:

Configuration config = HBaseConfiguration.create();
config.set("hbase.zookeeper.quorum", "localhost");  // Here we are running zookeeper locally

If multiple ZooKeeper instances make up your ZooKeeper ensemble, they may be specified in a comma-separated list (just as in the hbase-site.xml file). This populated Configuration instance can then be passed to an HTable, and so on.